Climate Change Adaptation Strategy

We know the climate is changing it has been since the planet first existed; it also sems that what the human population is doing and has done since the industrial revolution has a minor impact upon that change, the cycles of climate change maybe accelerated and perhaps more drastic, but that change is not unexpected as we can see the evidence in the past of such cycles occurring.  London in it's future will flood, freeze and scorch; lets spend the time figuring out what order and when and build/plan to that; why spends billions on flood defence when we could perhaps re-locate to safer areas much as it may be difficult to acknowledge.  We know that cities and countries in the past have been lost to forces of nature; surely its better to plan to avoid rather than fight such inevitable forces?